Fix quantization metadata: top-level bits 2 (matches tensor data)

config.json

@@ -55,7 +55,7 @@
   "model_type": "gemma4",
   "quantization": {
     "group_size": 64,
-    "bits": 4,
+    "bits": 2,
     "mode": "affine"
   },
   "quantization_config": {
@@ -201,4 +201,4 @@
     "use_clipped_linears": true
   },
   "vision_soft_tokens_per_image": 280
-}
+}